Re: Bug? Kernel doesn't prevent multiple rw nilfs mounts

[Michael Conrad <mconrad-HsDW+lVSy7tZ66HEZ9PjWw@public.gmane.org>]

On 10/24/2013 9:38 PM, Ryusuke Konishi wrote:
>> The double-mount should be prevented at the kernel level, right?  I
>> could try a linux version direct from kernel.org, next.
>>
>> If the double-mount should be prevented in user-space, then I could
>> check things like the libc, compiler, strace, etc.
> The double-mount check is done in user-space to avoid that two garbage
> collectors run on the same device.  Actually, nilfs kernel module
> itself can have two writable mounts.
>
> Nilfs-utils has two separate mount programs.  One is the version
> using libmount library (nilfs-utils/sbin/mount/mount_libmount.c)
> and another is prior mount program (nilfs-utils/sbin/mount/mount.c).
>
> Recent distros use the former program because the prior mount program
> does not work when /etc/mtab is a symbolic link to /proc/mounts.

Ah-ha!  Both systems use a symlink.  On System 1, I compiled nilfs-tools 
in a chroot so I could link them statically with recent library 
versions, then installed the static binaries.  Your configure script 
would not have been able to see the /etc/mtab symlink.

However, System 2 had recent libraries and I was able to "emerge 
nilfs-tools" normally.  However, that Gentoo ebuild was marked 
experimental, so maybe they know of the problem.  I'll investigate which 
source file was used for mount.nilfs2

Thanks for the information!

-Mike
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